Poor parents may even be fully convinced of the benefits of immunization—but these benefits will accrue sometime in the future, while the cost is incurred today. It makes sense, from today’s perspective, to wait for tomorrow. Unfortunately, when tomorrow becomes today, the same logic applies. Likewise, we may want to postpone the purchase of a bed net or a bottle of Chlorin until later, because we have better use for the money right now (there is someone frying delicious conch fritters across the street, say). It is easy to see how this could explain why a small cost discourages the use of a
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